Duct blank seam and apparatus for making a duct blank seam

ABSTRACT

A flanged duct blank has a male part defined by lead notches formed at each side of a leading end and has a female part defined by trail notches formed at each side of a trailing end. The male part includes a lock tab. The female part includes a leg part and a Z-bend. The Z-bend includes a leg part and a gap. The duct blank is repeatedly clamped and bent by a pivoting wiper to form a duct portion. The pivoting wiper includes a clench tool that has a retractable rib and a retractable roller. With the lock tab inserted into the Z-bend and the retractable rib engaged with the Z-bend, the retractable roller clenches the leg part over the lock tab to lock the male and female parts together in a duct seam.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/591,070 filed on Jan. 7, 2015, which is a divisional of U.S. patentapplication Ser. No. 13/959,999 filed Aug. 6, 2013 (U.S. Pat. No.8,950,229 issued on Feb. 10, 2015), which is a divisional of, and claimspriority to U.S. patent application Ser. No. 12/511,125 filed on Jul.29, 2009 (U.S. Pat. No. 8,561,448 issued on Oct. 22, 2013), which is acontinuation-in-part of, claims priority to, U.S. patent applicationSer. No. 12/243,489, filed on Oct. 1, 2008 (U.S. Pat. No. 8,276,425issued on Oct. 2, 2012), all of which are hereby incorporated byreference in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to ventilation ducts, and moreparticularly, to methods and apparatus for making ventilation ducts.

BACKGROUND OF THE INVENTION

With known apparatus for manufacturing ventilation ducts and the like, aseries of bends are made in a metal web to form a duct blank. The ductblank then is closed by one or more seams extending the length of theduct blank. The seams can be folded or welded shut.

A seam can be pre-formed by bending and aligning free edges of thepartially formed duct. However, known seams must be clamped,backstopped, or otherwise supported from an inner surface of the ductblank in order to properly apply the forces required for adequateclosure. Such clamping is not easily provided in-line with apparatus forbending the duct blank. Thus, the duct blank typically is removed fromthe bending apparatus to another work station for final closure of theseam. Removal of the duct blank to the other work station requires extrasteps for handling and aligning the duct blank in the other workstation. These extra steps reduce the efficiency of production.

Once the duct blank is removed from the bending apparatus, the seam canbe closed by repeatedly banging a hammer against the free edge of theseam. However, the repeated impacts of the hammer are noisy and tend todeform the metal along the seam. Alternatively, Welty (U.S. Pat. No.5,189,784 hereby incorporated herein by reference in its entirety)discloses an apparatus for forming and closing seams in box-shapedducts. However, Welty's apparatus is not adapted for use in-line withother machinery. In particular, manual handling is required to properlyposition a duct blank relative to Welty's clamps and rollers. Thus,Welty's apparatus, although a significant advance in the art of its day,fails to optimize efficiency of production.

SUMMARY OF THE INVENTION

In view of the unsolved problems posed by the prior art, it is a generalobject of the present invention to provide a lock seam structure thatpermits in-line forming and finishing of a duct blank seam to provide anease of manufacture not achieved with present duct structures. Anotherobject of the present invention is to provide a lock seam structure thatpermits in-line closure and finishing of a duct blank having edgeflanges. Another object is to provide a lock seam structure that permitsin-line finishing by clenching together male and female portions of aduct blank seam.

In one embodiment, the present invention comprises a duct blank formedfrom a sheet of bendable material, the duct blank having a body withflanges formed along side edges thereof, and with a male portion and afemale portion formed at opposed ends thereof, the male and femaleportions being shaped to be fitted together in a seam to close the ductblank, and the flanges being notched to permit bending the duct blank soas to form the seam.

In another embodiment, the present invention comprises a plurality ofsimilar duct blanks disposed along a continuous coil or web of sheetmetal, the duct blanks being demarked by paired lead and trail notchesformed at side edges of the metal sheet web, the same lead and trailnotches also defining the male and female portions of each duct blank.

These and other advantages of the present invention will be betterunderstood in view of the Drawings and description of a preferredembodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top or plan view of a schematic diagram illustrating a lineof equipment including an apparatus for forming a box-shaped ductaccording to the principles of the invention.

FIG. 2 is a side elevational view schematically showing the line ofequipment for carrying out the method of the invention.

FIG. 3 is a perspective view of a duct blank formed in a metal sheetwith male and female portions at leading and trailing ends and joined atthe trailing end to a similar duct blank.

FIG. 4 is a plan view of a main notcher die used in forming the male andfemale portions of the duct blank shown in FIG. 3.

FIG. 5 is an end view of the metal sheet with marked locationscorresponding to dimensions of the main notcher die shown in FIG. 4.

FIG. 6 is an end view of the duct blank of FIG. 3, bent to insert themale portion into the female portion and held by a clench tool portionof the forming apparatus of FIGS. 1 and 2, with the trailing end alignedto shear blades.

FIG. 7 is a perspective view of the duct blank of FIG. 3, bent to formflanges, a lock tab, and a Z-bend, and of a trailing duct blank.

FIG. 8 is an enlarged view of the Z-bend part of the duct blank shown inFIG. 7.

FIG. 9 is an end view of the Z-bend shown in FIG. 9.

FIG. 10 is an enlarged end view of the Z-bend shown in FIG. 9, with thelock tab inserted into the Z-bend.

FIG. 11 is an enlarged end view of a duct portion formed from the ductblank shown in FIGS. 8-13.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, an apparatus 10 produces box-shaped ductsections from a metal sheet 12, or other bendable material, of thedesired gauge and width. As is well known to those skilled in the art,the width of the metal sheet determines the length of the completed ductsection.

The metal sheet is commonly supplied on a large roll or coil 14, whichis placed in an uncoiler 16 at one end of the apparatus. The metal sheetis fed by a feeder 18 from the uncoiler into a straightener 22containing a plurality of rolls for removing the set in the metal sheetcaused by it being wound on a coil.

After the straightener, the metal sheet passes along a mid-line of theapparatus to main notchers 24 and intermediate notchers 26.

The notchers are controlled to notch the side edges of the metal sheetat predetermined distances to define a duct blank 28 that willultimately be bent to form the box-shaped duct section. In other words,the distance between the notches will correspond to the dimensions ofthe finished duct section. Referring to FIG. 3, at a leading end 32 ofthe metal sheet, the main notchers form opposed lead notches 34 in theside edges, defining a male portion 36 of the duct blank. As the metalsheet passes the intermediate notchers, opposed pairs of intermediatenotches 38 are formed at intervals along the side edges to define foldlines 42. After the last pair of intermediate notches, the main notchersform opposed pairs of trail notches 44, slots 46 extending partiallyinward across the metal sheet, and a second opposed pair of lead notches34′. The trail notches define a female portion 48 of the duct blank. Theslots define a trailing end 52 of the duct blank. The second pair oflead notches define a male portion 36′ of a trailing duct blank 28′.

Referring to FIGS. 4 and 5, each of the main notchers includes a die 242and a matching punch (not shown). The die opening has a leading face244, a trailing face 246, an inward face 248, and a slot 252. In use,the metal sheet is fed across the die so that a side edge of the metalsheet is in registration with a guideline 254. Operation of each mainnotcher punch and die produces the lead and trail notches at thecorresponding side edge of the metal sheet, defining inward notch edges248′ and slot ends 252′.

Once the metal sheet has been notched to form the duct blank, the sideedges are bent downwardly by a roll former 54 (shown in FIGS. 1 and 2),along side lines 56 defined by the inward notch edges, to form flanges58 extending substantially perpendicular to a main part 60 of the ductblank. The flanges are later used to connect individual box-shaped ductsections, as is well known to those skilled in the art. It will beunderstood that the principles of the invention are applicable toforming box-shaped duct sections regardless of whether these flanges areformed or not.

Referring back to FIGS. 1 and 2, the duct blank is then fed into aforming apparatus 62. The forming apparatus and its operation aredescribed more fully in co-pending U.S. patent application Ser. No.12/243,489, hereby incorporated herein by reference in its entirety. Asdiscussed therein, the forming apparatus includes a clamp beam 64, a bedassembly 66, and a wiper 68, as shown in FIG. 6. The wiper and the clampbeam together provide a vertically opposed pair of upper and lower shearblades 72, 74. The wiper includes a clench tool 76 for closing a seamformed in the duct blank, as further described in detail below.

Referring to FIG. 6, the clench tool includes a retractable rib 78extending across the width of the wiper, and also includes a retractableroller assembly 82 disposed between the retractable rib and the shearblade of the wiper. The retractable roller assembly is movable acrossthe wiper substantially parallel to the retractable rib.

Referring to FIGS. 7 through 11, in the forming apparatus, the ductblank is repeatedly folded at the lead and trail notches so that theduct blank male portion is bent substantially perpendicular to the ductblank main part to form a lock tab 84, and so that the duct blank femaleportion is folded to form a Z-bend 86, an offset part 88, and a leg partextending from the Z-bend to the duct blank trailing end. The lock tabprotrudes from the main part to a length L_(M). The leg part extends alength L_(L) between the duct blank trailing end and the Z-bend. Thelength L_(L) exceeds the length L_(M).

Referring specifically to FIGS. 8 and 9, the Z-bend has a first inwardfold 94 adjacent to the leg part and has a first outward fold 96disposed inward of the inward fold. Between the inward and outwardfolds, a second inward fold 98 forms an insertion angle 102 openingtoward the trailing end of the duct blank.

The offset part has an outward bend 104 and an inward bend 106. Theoutward and inward bends together bring the outer surface 108 of the legpart into substantial alignment with the outer surface 112 of the ductblank. The outward bend and the inward bend are spaced apart so as toform a gap 114 between the Z-bend inward fold and the duct blank mainpart.

Referring to FIGS. 9 and 10, in the forming apparatus, the duct blank isfolded at the intermediate notches so that the lock tab is inserted intothe Z-bend adjacent to the leg part. The insertion angle is proportionedto receive and guide the lock tab into the Z-bend.

Referring to FIG. 11, after the lock tab has been inserted into theZ-bend by operation of the forming apparatus, the wiper then is pivotedupward to form an approximately twenty (20) degree lock bend 116 in theleg part adjacent to the duct blank male portion. Referring back to FIG.6, the duct blank then is advanced so that the duct blank trailing endis in registration with the shear blades, and the retractable rib isextended from the wiper to engage the gap between the Z-bend and theduct blank main part. Thus, the duct blank is held with the trailing endand the opposed inward slots registered to the shear blades.

The wiper then is moved against the clamp beam so that the shear bladessever the duct blank from the metal sheet at the trailing end defined bythe opposed inward slots. While the retractable rib continues to engagethe Z-bend gap, the retractable roller assembly then is extended andmoved across the wiper so as to clench the leg part over the main partadjacent to the lock tab, thereby securing the lock tab into the Z-bendto form a finished duct portion 118. Once the leg part has beenclenched, the retractable rib is withdrawn from the gap, releasing thefinished duct portion.

As a particular advantage of the present invention, the insertion angleenables automated insertion of the lock tab into the female portion withimproved reliability. The offset part enhances ease of closure of thelock seam by providing a substantially smooth outer surface thatenhances uniformity of a bending force exerted on the leg part throughthe female portion. Additionally, the offset part enables forming theinsertion angle while maintaining a substantially smooth outer surfaceof the duct blank near the finished lock seam. Also, the offset allowsfor engagement of a holding bar or clench die with the outer surface ofthe duct blank female portion. Engagement of a clench die permitsclenching shut the lock seam, thereby providing a substantially smootherduct portion than can be obtained with a rolled lock seam. Thus, whilethe duct blank is held in the forming apparatus, the leg part can bebent to a position substantially flat against the outer surface,providing an attractive smooth appearance to the duct portion. As theleg part already has been bent to lock the seam, the duct portion can behandled for removal from the apparatus without concern for the maleportion springing out from the female portion of the seam.

Although this invention has been shown and described with respect to thedetailed embodiments thereof, it will be understood by those skilled inthe art that various changes in form and detail thereof may be madewithout departing from the spirit and the scope of the invention.

What is claimed is:
 1. A sheet of bendable material for constructioninto a duct body, comprising: a leading end; a trailing end; side edgesextending rearward from the leading end to the trailing end; a pluralityof lead-and-trail notches formed in the side edges at predeterminedintervals, each of the lead-and-trail notches extending from the sideedges and towards a centerline of the sheet of bendable material,thereby defining a bend line substantially aligned with the side edges;a plurality of cut slots formed in the side edges, each of the cut slotsextending from said bend line and towards the centerline of the sheet ofbendable material; wherein said leading end defines a male seam portion,and said trailing end defines a female seam portion, said female seamportion capturing said male seam portion when said leading end and saidtrailing end are joined to one another to form said duct body; andwherein said male and female seam portions are formed parallel to saidleading end and said trailing end.
 2. The sheet of bendable materialaccording to claim 1, further comprising: intermediary notches indentedinto the side edges between said lead-and-trail notches, each of theintermediary notches extending to said side bend line.
 3. The sheet ofbendable material according to claim 1, wherein: each of saidlead-and-trail notches includes a slot extending inward across saidsheet from said inward edge to an inward end, each of the slots defininga shear line across said sheet, the shear lines dividing saidlead-and-trail notches into lead notches and trail notches.
 4. The sheetof bendable material according to claim 3, wherein: each of said trailnotches has a lead part and a trail part, the lead and trail partsextending from one of said side edges across the width of an adjacentflange, the slots defining said trail notches being disposed between thelead part and the trail part, the slots extending partway across saidsheet toward the opposed trail notch.
 5. The sheet of bendable materialaccording to claim 4, wherein: said bendable material is metal.